rather nice confirmation of expectation going back in time. how big will a sphere of creation become after 14 billion years. It is expanding sublight. Much slower than light speed. how big can such a bubble become in 14 billion years?
now suppose my reflection hypotgesis hold true. Than the actual bubble may only be two to three times our Galactic radii or 100,000 light years for sake of discussion.
that is 140,000 reflection cycles painting our current picture. all ball park at the moment
Evidence for the First Generation of Stars
Schematic illustration of the progenitor of a supermassive black hole in the form of a supermassive star. After the accretion of gas into the supermassive star ends, the star contracts, ignites hydrogen burning, and re-expands into a late phase of instability. Pulsation-driven mass loss then proceeds through discrete ejection episodes that remove weakly-bound envelope material. Earlier shells expand to large radii, whereas the final pre-collapse ejection remains compact and dense, setting the immediate circumstellar environment which explains Webb telescope data on the observed population of `little red dots’. The ejecta carries a characteristic abundance pattern which is consistent with spectroscopic observations by the Webb telescope. The supermassive star then continues toward collapse through a General Relativistic instability owing to Einstein’s gravity and ultimately ends as a heavy black-hole seed for a quasar. (Image credit: Devesh Nandal et al. 2026)
Two new papers today provide evidence for the first generation of stars, made solely from the primordial gas of hydrogen and helium left from the Big Bang. Middle-aged stars like the Sun recycle material that was already processed through nuclear fusion in the interiors of stars. However, the primordial material that made the first stars had no heavy elements. As a result, it did not cool efficiently and condensed into massive stars. The first stars with masses exceeding ten solar masses, had a surface temperature of up to 10⁵ degrees and acted as efficient factories of ultraviolet radiation.
This was a theoretical prediction that I derived with my students and postdocs at Harvard University thirty years ago. The earliest publications included a paper, accessible here, that I co-authored with my former postdoc Volker Bromm and Rolf Kudritzki in 2001. Our calculations demonstrated that the ultraviolet radiation from the early stars would break hydrogen and helium atoms in their vicinity, and result in the emission of a distinct spectral line from a singly-charged helium ion at a wavelength of 0.1640 micrometers, labeled He II λ1640. The theoretical predictions from my research were summarized in two textbooks that I published a decade later, titled: “How Did the First Stars and Galaxies Form?” and “The First Galaxies in the Universe”.
Recent spectroscopic observations by the Webb Telescope detected the emission of a strong He II λ1640 spectral line in the vicinity of an early galaxy, labeled GN-z11, at a cosmological redshift of z=10.6. This galaxy existed 13.4 billion years ago, just 400 million years after the Big-Bang. No heavy elements were identified in its spectrum. The properties of the spectral-line source, labeled Hebe, can be explained by a cluster of the first-generation stars. A new paper, posted here, studies an alternative source for the ultraviolet radiation in the form of an accreting supermassive black hole. The authors show that a star cluster with a total mass of 10⁵ solar masses can explain the data more naturally. Such a cluster of first generation of stars constitutes the limit of what is expected in theoretical calculations dating back to my work with Bromm and Kudritzki.
My interest in this topic started as early as in 1994, shortly after my arrival as junior faculty at Harvard, when I published a paper — accessible here — with Fred Rasio, suggesting that the progenitors of the first supermassive black holes at the centers of galaxies are supermassive stars. Our model suggested that as a result of inefficient cooling, a clump of primordial gas would generically condense at the center of the first galaxies without fragmenting into low-mass stars. The collapse of this primordial cloud would result in a supermassive star that lives for about a million years and eventually collapses to a seed of a quasar black hole. The early population of quasars are known to be black holes which accrete gas at the center of galaxies. Bright quasars peaked in abundance during the first few billion years after the Big-Bang.
Other observations by the Webb telescope reveal the existence of a population of `little red dots’, compact reddish galactic cores which existed during the era of quasar formation. Could these `little red dots’ be the seeds of quasar black holes? This was indeed the suggestion we made in a paper that I recently published in collaboration with Fabio Pacucci, accessible here.
But there is another new paper that I co-authored today, available here, which was led by my postdoc Devesh Nandal. The paper explains that the spectral properties of `little red dots’ requires dense gas close to the source, yet the physical origin of that cocoon-like structure remains unclear. Our paper shows that late-time episodic mass-loss from supermassive stars leads to the required dense gas cocoons.
After the accretion of gas into the supermassive star ends, the star contracts, ignites hydrogen burning, and re-expands into a late phase of instability. Pulsation-driven mass loss then proceeds through discrete ejection episodes that remove weakly-bound envelope material. The earlier shells expand to large radii, whereas the final ejection remains compact and dense, setting the immediate circumstellar environment relevant to the `little red dot’ phase. The ejecta carries a characteristic abundance pattern which is consistent with spectroscopic data from the Webb telescope. The supermassive star then continues toward a General Relativistic instability and ultimately collapses into a heavy black-hole seed owing to Einstein’s gravity.
Our paper examines five models with different abundances of heavy elements, all having progenitor masses of order 10⁵ solar masses. We followed the evolution of these supermassive stars after they stopped accreting gas with radial pulsations calculations and general relativistic stability diagnostics. Mass loss during the final stages of evolution occurs not as a steady wind, but through discrete strange-mode ejection episodes. In the nearly pristine gas case, there were four late episodes that lasted 41 to 282 years and ejected 10 to 348 solar masses each, for a total loss of 480 to 1,000 solar masses. The final episode alone contributes 73% of the mass-loss, and leaves behind a compact, opaque shell extending out to a light-year that reproduces the dense gas cocoons in `little red dots’.
The final ejecta is dominated by hydrogen and helium but is also rich in nitrogen, as observed in `little red dots’. A supermassive star reaches the General Relativistic instability at an age of about a million years and eventually collapses within a few hours, retaining almost all of its mass.
All in all, these calculations demonstrate that supermassive stars provide a physically motivated origin for the compact cocoon-like structure associated with `little red dots’, while remaining the natural progenitors of massive black hole seeds for quasars.
It took 32 years to confirm my early conjecture with Fred Rasio on this subject, but the journey was definitely worthwhile. I regard 32 years as a discounted wait time. After all, according to the Old Testament, the Israelites spent 40 years wandering in the desert before reaching the promised land. No doubt that technology works in speeding up progress, as is the case with the Webb telescope data. If the Israelites had access to GPS systems, they would have reached the Promised Land in a matter of months.
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